#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <string>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <fstream>
#include <cassert>
#include <cstring>
#include <unordered_set>
#include <unordered_map>
#include <numeric>
#include <ctime>
#include <bitset>
#include <complex>
#include <random>
using namespace std;
const int N = 3001;
int a[N][N];
int read() {
char c;
cin >> c;
if (c == 'R') return 0;
if (c == 'G') return 1;
if (c == 'W') return 2;
assert(false);
return -1;
}
int n, m;
int ok(int i, int j, int dir) {
if (dir == 0) {
if (i == 0 || i + 1 == n) return 0;
return a[i - 1][j] == 0 && a[i][j] == 1 && a[i + 1][j] == 2;
} else {
if (j == 0 || j + 1 == m) return 0;
return a[i][j - 1] == 0 && a[i][j] == 1 && a[i][j + 1] == 2;
}
}
vector<pair<int, int>> gt(int i, int j, int dir) {
if (dir == 0) {
return {{i - 1, j}, {i, j}, {i + 1, j}};
} else {
return {{i, j - 1}, {i, j}, {i, j + 1}};
}
}
bool inter(vector<pair<int, int>> &x, vector<pair<int, int>> &y) {
for (auto f : x) {
for (auto s : y) {
if (f == s) return 1;
}
}
return 0;
}
vector<vector<int>> g;
vector<int> used;
vector<int> clr;
void dfs(int v, int c) {
clr[c] = 1;
used[v] = 1;
for (auto t : g[v]) {
if (!used[t]) dfs(t, c ^ 1);
}
}
pair<int, int> parse(int v) {
v %= n * m;
return {v / m, v % m};
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> n >> m;
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
a[i][j] = read();
}
}
vector<int> tk;
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
if (ok(i, j, 0)) tk.push_back({i * m + j});
if (ok(i, j, 1)) tk.push_back({i * m + j + n * m});
}
}
auto get = [&](int x) {
int v = tk[x];
int tp = (v / (n * m));
v %= n * m;
int i = v / m;
int j = v % m;
return gt(i, j, tp);
};
g.resize(tk.size());
used.resize(tk.size());
clr.resize(tk.size());
for (int i = 0; i < (int)tk.size(); i++) {
for (int j = i + 1; j < (int)tk.size(); j++) {
vector<pair<int, int>> f = get(i);
vector<pair<int, int>> s = get(j);
if (inter(f, s)) {
g[i].push_back(j);
g[j].push_back(i);
auto x = parse(tk[i]);
auto y = parse(tk[j]);
assert(abs(x.first - y.first) + abs(x.second - y.second) == 2);
}
}
}
int f = (int)(tk.size());
if (f > 20) {
cout << "zopa" << endl;
exit(0);
}
int ans = 0;
for (int mask = 0; mask < (1 << f); mask++) {
int ok = 1;
for (int i = 0; i < f; i++) {
if (((mask) >> i) & 1) {
for (auto j : g[i]) {
if ((mask >> j) & 1) ok = 0;
}
}
}
if (ok) ans = max(ans, __builtin_popcount(mask));
}
cout << ans << endl;
}
